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Utilizing ammonia as a co-firing fuel to replace amounts of fossil fuel seems a feasible solution to reduce carbon emissions in existing pulverized coal-fired power plants. However, there are some problems needed to be considered when treating ammonia as a fuel, such as low flame stability, low combustion efficiency, and high NO x emission. In this study, the co-firing characteristics of ammonia with pulverized coal are studied in a drop tube furnace with staged combustion strategy. Results showed that staged combustion would play a key role in reducing NO x emissions by reducing the production of char-NO x and fuel(NH 3)-NO x simultaneously. Furthermore, the effects of different ammonia co-firing methods on the flue gas properties and unburned carbon contents were compared to achieve both efficient combustion and low NO x emission. It was found that when ammonia was injected into 300 mm downstream under the condition of 20% co-firing, lower NO x emission and unburnt carbon content than those of pure coal combustion can be achieved. This is probably caused by a combined effect of a high local equivalence ratio of NH 3 /air and the prominent denitration effect of NH 3 in the vicinity of the NH 3 downstream injection location. In addition, NO x emissions can be kept at approximately the same level as coal combustion when the co-firing ratio is below 30%. And the influence of reaction temperature on NO x emissions is closely associated with the denitration efficiency of the NH 3. Almost no ammonia slip has been detected for any injection methods and co-firing ratio in the studied conditions. Thus, it can be confirmed that ammonia can be used as an alternative fuel to realize CO 2 reduction without extensive retrofitting works. And the NO x emission can be reduced by producing a locally NH 3 flame zone with a high equivalence ratio as well as ensuring adequate residence time. [ABSTRACT FROM AUTHOR]

The advancement of co-processing solid wastes in coal-fired boilers is significant for waste recycling and contributes to the sustainable development of the coal-fired power industry. However, concerns over the emission of dioxins during co-processing have prompted a comprehensive investigation into the dioxin emission properties. In this study, the PCDD/F emission concentrations of seven coal-fired boilers, including three pulverized coal boilers and four circulating fluidized bed boilers were examined. The results indicate that co-processing solid wastes in coal-fired boilers did not lead to an increase in the mass concentration of dioxins in either the flue gas or solid samples, and the international toxic equivalents (I-TEQ) of dioxins in the flue gas complied with prevailing emission standards (0.1 ng I-TEQ/Nm3) in China, proving that coal-fired boilers co-processing would not raise the emission risk of dioxins. The types of waste during co-processing had minimal effect on the I-TEQ of dioxins. A significant proportion of PCDD/Fs was observed in the ash samples, while only 13.0–25.7% and 0.7–6.8% of dioxins were distributed in the boiler slag and the flue gas, respectively. The emission factor of dioxins under the blank conditions ranged from 0.009 to 0.327 ng I-TEQ/kg-coal, while it ranged from 0.015 to 0.129 ng I-TEQ/kg-(coal+waste) under the co-processing conditions. The reduction of emission factor under co-processing condition could be attributed to the significant decrease of dioxins I-TEQ. [Display omitted] • Co-processing wastes in boilers did not lead to an increase in the I-TEQ of dioxins. • The type of waste during co-processing had minimal effect on the I-TEQ of dioxins. • A significant proportion of PCDD/Fs was observed in the ash samples. • The emission factor of dioxins ranged from 0.015 to 0.129 ng I-TEQ/kg-(coal + waste). [ABSTRACT FROM AUTHOR]

Energy is a critical component in any given region's growth. India has the world's fourth-largest coal reserves. Therefore, energy generation from coal-based power plants is still a significant source of power in the country. However, the performance of Indian coals is poor compared to foreign coals such as South African, Indonesian, and US coals due to the high ash and moisture content. Seventy percent of country electricity need is still dependent on coal power even with known negative environmental consequences such as the production of CO 2 & greenhouse gases, and air pollution caused by SO x , NO x , coal sludge, coal dust, and by-products of coal combustion. In this work, effect of coal types, particle sizes, and furnace temperatures on the ignition delay time of pulverized coal particle is investigated. In the current study, the ignition delay time of four Indian coals (IS1, IS2, IS3, and IS4), two Indonesian coals (IAS1 and IAS2), and one South African coal (SA1) were examined for particle sizes ranging from 35 to 115 µm, furnace temperature ranging from 1000 to 1700 K, and oxygen concentrations ranging from 12 to 20% in gas. Furthermore, ignition delay analysis of different coal mixtures (Indian and foreign coals mixtures) has also been studied. Numerical analysis of ignition delay time has been performed using MATLAB. Results show that the ignition delay time of coal particles increases with a decrease in furnace temperature and an increase in particle size. Results also show that the Indian coals have a larger ignition delay time than other considered coals, and ignition characteristics of Indian coals can be enhanced by mixing with high-grade ones. An increase in oxygen concentration also reduces the ignition delay time of the coals. [ABSTRACT FROM AUTHOR]

This study aimed to verify the role and feasibility of co-fired fly ash (CFA) as an alternative construction material. It also demonstrated the engineering properties of CFA mortar and compared them with those of pulverized coal fly ash (PCFA) mortar. Further, CFA-PCFA-cement mortar specimens were mixed to produce ternary eco-binder mortars and find the optimal application proportion. The results pointed out that the pozzolanic strength activity index of CFA was 76 %, with only a slight pozzolanic reaction. The sum of the chemical composition (SiO 2 +Al 2 O 3 +Fe 2 O 3) of CFA was insufficient to meet ASTM C618 requirements, and it was deduced that a small amount of CFA should be used as the substitute for cement or fine aggregates. Specimens with CFA replacing fine aggregates contributed to lower water absorption, improved sulfate resistance, and increased compressive strength; Specimens with CFA replacing cement reduced shrinkage and improved sulfate resistance but decreased compressive strength and increased absorption. Blended CFA-cement mortars consisting of 5 % CFA as a replacement material for cement and fine aggregates had excellent engineering properties. Ternary blended CFA-PCFA-cement mortar exhibits superior engineering properties. The optimum proportion is an economy-friendly binder composed of 10 % CFA (5 % as cement and 5 % as fine aggregates) and 10% PCFA (as a replacement for cement). • Development and application of ternary economic binders in this study. • Ternary eco-binder consists of co-fired fly ash (CFA), pulverized coal fly ash (PCFA) and cement. • CFA is classified as a low pozzolanic reactive material. • Eco-binder consists of 5 % CFA as cement, 5 % CFA as fine aggregates and 10 % PCFA as cement. [ABSTRACT FROM AUTHOR]

The generation and transport of coal powder has caused great harm to coal reservoir channeling conductivity, affecting the capacity of coalbed methane wells, causing the failure of engineering equipment and great distress to production, while current unblocking methods have many shortcomings. Dispersants, foam stabilizers, and inorganic salt electrolytes were selected in this study as the main components of blockage removal agents, and the wettability and synergistic effects of each component were tested. The results showed that the wettability was best when the ratio of the blockage removal agent was 0.8% SDS + 0.6% BS-12 + 0.8% NaCl, which was 1.57 times higher than that of a single dispersant. The surface tension of blockage removal agent was 64.75% lower than that of clear water. The discharge rate of the pulverized coal particles under the action of the optimum blockage removal agent reached more than 40%, which was more than twice that of clear water. The discharge of the pulverized coal was more than 1.2 times that of the common dispersant formula. The gas-liquid permeability was 4.21 times higher than that obtained with water injections, and 1.45 to 2.91 times higher than that of the commonly used dispersant formulations. This work is helpful to provide a practical guide for the efficient cleaning of sedimentary retained pulverized coal in low-yield coalbed methane wells. This research result is very important to ensure the efficient and stable development of coalbed methane. [Display omitted] • The optimal ratio of blockage removal agent was studied. • Pulverized coal intrusion into fracture experiments were carried out. • Different blockage removal agent solutions studied by previous researchers were compared. • The problem of pulverized coal accumulating and seizure in support cracks is solved. • Guidance for improving gas-liquid permeability and CBM wells extraction effect. [ABSTRACT FROM AUTHOR]

Phenol constitutes one of the main pollutants in wastewater. In the present study, adsorption with the use of a cheap alternative bio-filtration medium (activated ceramic, AC) was carried out to remove organic (phenol) and inorganic metals, such as zinc (Zn+2), copper (Cu+2), and lead (Pb+2). Activated ceramic was modified by ozonation with a mixture of crushed coal, Kaolin, and Bentonite, which were thermally treated in a vacuum furnace at temperatures ranging between 300 °C and 600 °C. The volume ratio of crushed coal to Kaolin to Bentonite was 4:6:1. This mixture was mixed with water by the volume ratio of 1:1. The mixture had been exposed to ozone before being used for activation. The pH measurements, chemical analysis, and FT-IR spectra were performed, and textural characterization was obtained. The influence of different parameters including different doses and contact times were investigated. For contact times of between 20 and 120 min, the removal efficiencies of phenol were 23% to 61%, and 56% to 79% with AC amounts of 5 g and 40 g, respectively. The Freundlich and Langmuir isotherm equations were used to explore the adsorption kinetics. The equilibrium data was found to best fit with both models. The use of AC for the removal of phenol showed a high removal efficiency of 85%, whereas the AC removes 67%, 59%, and 41% of Pb+2, Cu+2, and Zn+2, respectively. [ABSTRACT FROM AUTHOR]

Copyright of Science of Sintering is the property of National Library of Serbia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

High-concentration H 2 S formed in the reduction zone of pulverized coal air-staged combustion can result into the high temperature corrosion of water wall tube of boiler, so it is of great importance to accurately predict H 2 S concentration for the safe operation of boilers and burners. H 2 S formation and evolution depends on two steps: the sulfur release from coal conversion and gas-phase reactions of sulfur species. In this study, the sulfur release characteristics from the pyrolysis of 17 coals, including 5 lignite, 9 bituminous coals and 3 anthracites, are investigated in a drop tube furnace (DTF). Sulfur release model is developed to describe the relationship between sulfur release and coal types. A global gas-phase reaction mechanism of sulfur species composed of ten reactions is used to calculate and predict the formation and evolution of H 2 S, COS and SO 2 in the reduction zone of pulverized coal air-staged combustion. A wide range of air-staged combustion experiments of 17 coals are conducted in the DTF at different temperatures and stoichiometric ratios to validate the developed model. The results show that the prediction errors of sulfur species, including SO 2 , H 2 S and COS, are within ± 30%, which indicates that the developed prediction model of sulfur species is of great assistance for CFD modeling of actual engineering application. [ABSTRACT FROM AUTHOR]

This paper analyzes the feasibility of co-burning biomass in an energy boiler operating on coal, without modifying the boiler, under the conditions of establishing an energy biomass crop. The use of biomass in an energy boiler aims to reduce greenhouse gas emissions and the costs of purchasing CO2 certificates. [ABSTRACT FROM AUTHOR]

A special characteristic of the coal bottom ash is the content of unburned carbon, due to incomplete combustion in the boiler furnace. A special, multi-objective procedure for separation of ash particles containing unburned carbon was developed with the purpose of obtaining synthetic graphite and it was presented in the first part of the paper. In order to achieve full recycling of the ash landfill content, various secondary waste materials resulting from separation and concentration phases of the process flow must be further processed and sorted in order to ensure properties that guarantee recyclability. The process flow presented incorporates the graphitization process flow in such way that all secondary waste fractions can be recycled in various directions. The fix carbon content (FCC) and the mass breakdown weight (MBW) were determined for each separation process in order to choose the optimal process flow. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Harbin Institute of Technology. Social Sciences Edition / Haerbin Gongye Daxue Xuebao. Shehui Kexue Ban is the property of Harbin Institute of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract In an experimental study the effects of varied oxygen concentrations in the oxidizer gas on resulting flow fields, combustion products and general behavior of pulverized coal swirl flames under oxy-fuel conditions have been investigated. Experiments were carried out in a small scale down-fired cylindrical combustion chamber equipped with an annular swirl burner. Studied flames had a constant power output of 40 kW th and O 2 /CO 2 oxidizer gas mixtures with O 2 concentrations ranging from 23 to 33 vol%. Detailed two-dimensional flow field measurements are obtained from laser Doppler anemometry (LDA). Velocity profiles (Mean and RMS) have been obtained for all conditions investigated and serve as basis for identification of flow field characteristics. Velocity RMS values are provided as supplementary material. To complement flow field measurements, in-flame gas composition measurements were also conducted using a sampling probe combined with infrared gas absorption analysis via Fourier-transform infrared (FTIR) spectrometry. The results obtained show increased velocities, particularly along the main vortex for flames with increased oxygen contents, while lower velocities are found to occur inside the recirculation regions. The opposite occurs with lower O 2 concentrations, showing significantly reduced velocities in the main vortex, but stronger recirculation than the high oxygen counterparts. This effect is attributed to a modification of the swirl level introduced by the expansion of product gases. Measured NO and CO in-flame concentrations showed significant variations under different O 2 concentrations in the oxidizer. [ABSTRACT FROM AUTHOR]

• Blending WCO to conventional fuels gave chance for applying heat energy fuel, investment for environment, economic enhancement and health protection. • Excited atoms inside the flame was affected with flame temperature and droplet size. • Microscopic thermal analysis was done using hyper-spectral camera. • Traditional heat energy measurement technique was applied. Flame spectroscopy for conventional fuels and their blends with waste cooking oil (WCO) wasn't carried out yet. In this research, WCO was blended with both light diesel oil (LDO) and heavy diesel oil (HDO) by 20% by mass, B1 and B2 respectively where no chemicals were added. Combustion processes were done by swirled vane burner inside and outside the water boiler at different heat loads. Axial plane flame temperatures were measured. The results showed that the highest peak thermal energy was achieved by HDO at all heat loads. Blend B2 produced lower heat energy than HDO by nearly average 7.5%. B2 produced lower heat energy transferred to water boiler than HDO by nearly 12.2%, 2.1%, 8.2 and 7.6% while B1 supplied 17%, 13.6%, 29.4% and 6.1% lower compared to LDO. LDO atoms are excited for long period along the flame length while WCO took short one. Both flame temperature and emission radicals of B1 were lower than that of LDO at the same condition and position. Fuel droplets size controlled the absorption of radiation energy for atom excitation. [ABSTRACT FROM AUTHOR]

• Copper/iron oxide carrier tested under autothermal conditions with natural gas. • Data presented from 11 h of continuous autothermal operation. • Natural gas conversion ranged from 70 to 90% during autothermal trials. • Attrition rate was around 0.45 kg/hr over 11 h in authothermal. • Baseline cost methodology presented to develop more advanced oxygen carriers. The United States Department of Energy is developing transformational fossil fuel combustion technologies that result in more efficient power cycles and/or substantial reductions in GHG emissions. Chemical Looping Combustion (CLC) has the potential to achieve a lower cost of electricity than a supercritical pulverized coal power plant with an amine absorption system. Although the concept and research on chemical looping has a long history, CLC has numerous technical issues that must be addressed prior to a commercial debut. This effort is directed toward the following major issues for CLC: (1) demonstrating continuous solids handling, operability, and reactor performance at autothermal conditions and (2) preliminary assessments of oxygen carrier attrition and relative material make-up costs. These are critical issues that should be addressed under realistic conditions prior to directing resources toward larger scale demonstrations. This paper will also describe NETL's small 50-kW th natural gas circulating CLC test facility located in Morgantown, WV. Despite its small size, this experimental test unit has operated at autothermal conditions for 11 h using a copper-iron-alumina oxygen carrier developed at NETL. This paper will describe the test facility and operating experiences using NETL's "Gen 2.0" oxygen carrier material. Natural gas conversion to CO 2 ranged from 70 to 90% over approximately 75 oxidation-reduction cycles during the autothermal operating period. Estimates for the process specific attrition rate during autothermal operation are also presented. Finally, estimates for the oxygen carrier makeup cost, specific to the NETL process configuration, are several orders of magnitude greater than the NETL target. Future work should focus on reducing the oxygen carrier material cost and improving the attrition resistance of the oxygen carrier material under autothermal test conditions. [ABSTRACT FROM AUTHOR]

• We develop a markup approach for the costs of power generation technologies. • The markup is a metric for use in multi-region multi-sector energy-economic models. • We provide standardized markups for technologies for different regions of the world. • Calculations are most sensitive to capital and fuel costs and capacity factors. • We apply our approach to project energy mixes for different future scenarios. Multi-region multi-sector energy-economic models are often used to analyze long-term scenarios of energy development, however, these models usually rely on a simplified representation of technological details in power generation. To strengthen this representation, we develop a method for modeling the economic competition between different advanced technologies in multi-region multi-sector dynamic energy-economic models based on a markup approach, which represents the measure of the cost of a technology relative to the price received for electricity generation. The markup includes capital costs, fixed and variable operating and maintenance (O&M) costs, fuel costs, and transmission and distribution (T&D) costs. For intermittent technologies, it also includes a backup requirement to make these technologies effectively dispatchable. For carbon capture and storage (CCS) technologies, it also includes the costs of CO 2 capture, transportation and storage. We provide a standardized markup calculation for generation technologies for different regions of the world, including USA, China, India, EU, Japan and others. Then we analyze the sensitivity of the calculation to critical inputs, including capital costs, fuel costs, carbon prices and capacity factors. We provide a detailed calculation of the relative costs of the following technologies: new pulverized coal, new pulverized coal with CCS, natural gas combined cycle, natural gas with CCS, biomass-fueled plant, biomass with CCS, advanced nuclear, wind (for small and medium penetration levels), solar, wind with backup (for large penetration levels), co-firing of coal and biomass combined with CCS, and advanced CCS on natural gas. For illustration, we incorporate the markups into the MIT Economic Projection and Policy Analysis (EPPA) model, a global multi-sector multi-sector dynamic energy-economic model with a detailed representation of power generation technologies, and run several scenarios. Our analysis and results provide insight on the deployment of different low-carbon power generation technologies depending on assumptions about carbon policy stringency. [ABSTRACT FROM AUTHOR]

For coal and gas dual-fired boiler, pulverized coal mass flow and gas volume flow into furnace are important criteria for boiler operation adjustment, and they are important input parameters for boiler performance analysis. However, different from the gas volume flow measurement technique that is mature, the measurement of pulverized coal mass flow is difficult, especially for the boiler equipped with middle storage pulverizing system. In order to solve this problem, an indirect measurement method through other operation parameters was put forward to obtain the pulverized coal mass flow. Its solving idea is to calculate the coal combustion and the gas combustion, in order to get the flue gas products corresponding to unit mass of coal and unit volume of gas respectively, and then obtain the pulverized coal mass flow by the flue gas products and the gas volume flow. This method solves the long-standing difficulty for pulverized coal mass flow, and has certain practical value. [ABSTRACT FROM AUTHOR]

Highlights • Greenfield PC plant with Calcium looping and sorbent storage assessed. • Sorbent storage allows reducing the size and cost of ASU, CPU and calciner. • Economic optimization performed for plants with weekly capacity factor of 55–67%. • In the assessed cases, the storage system reduces the cost of CO 2 avoided by 16–25%. Abstract In this work, a Calcium looping (CaL) system including high temperature sorbent storage is presented, allowing to reduce the size of the calciner and the associated capital-intensive equipment (ASU and CPU). Reduction of the capital costs is particularly important for power plants with low capacity factors, which is becoming increasingly frequent for fossil fuel power plants in electric energy mixes with increasing share of intermittent renewables. The process assessment is performed by: (i) defining pulverized coal power plant (PCPP) with CaL capture system with and without sorbent storage and their mass and energy balances at nominal load; (ii) defining a simple method to predict the performance of the plant at part-load; (iii) defining the economic model, including functions for the estimation of the plant equipment cost; (iv) performing yearly simulations of the systems to calculate yearly electricity production, CO 2 emissions and levelized cost of electricity for different sizes of the calcination line and the storage system and (v) performing sensitivity analysis with different power production plans and carbon taxes. With this process, optimal size of the calciner and of the storage system minimizing the cost of electricity have been found. The optimal plant design was found to correspond to a solids storage system sized to manage the weekly cycling and a calciner line sized on the average weekly load. However, to avoid excessively large solids storage system, sizing the calciner on the average daily load and the storage system to manage the daily cycling appears more feasible from the logistic viewpoint and leads to minor economic penalty compared with the optimal plant design. For the selected case sized on the daily cycling, reduction of the cost of CO 2 avoided between 16% and 26% have been obtained compared to the reference CaL plant without solids storage, for representative medium and low capacity factor scenarios respectively. [ABSTRACT FROM AUTHOR]

Highlights • A full-scale oxy-fuel cement rotary kiln of 3,000 ton/year clinker capacity has been numerically investigated. • The CFD study was part of an iterative optimization procedure with the process modelling of the whole cement plant with full oxy-fuel capture. • The optimal rotary kiln operating conditions has an oxygen concentration of 52.1% in the primary oxidizer stream. Abstract Oxy-fuel combustion has been shown to be an attractive technology to be implemented in cement production with CO 2 capture from a process point of view. Due to the market situations and future perspectives it is necessary that the technology can be retrofitted into existing plants. As part of the H2020 EU project CEMCAP, the study presented here investigates the retrofitting of oxy-fuel combustion technology on a typical full-scale cement rotary kiln of 3000 ton/year clinker capacity. The flame generated by a commercial burner has been modelled by CFD with a seven steps combustion reaction model, the k-omega SST turbulence model, and the discrete ordinates radiation model with the Weighted Sum Grey Gas model. The burner is composed of an annular outlet where coal is fed and nozzles from which angled high velocity jets generate a swirling motion for flame stabilization and mixing purposes. As in all rotary cement kilns, a high temperature low velocity secondary oxidizer stream coming from the clinker cooler flows coaxially to the burner in the kiln for heat efficiency purposes. A flame developing in air has been used as a reference case and several oxy-fuel flames have been characterized and compared. The oxy-fuel inlet parameters that are varied in the study are the oxidizer composition and flow rates in both the primary and secondary streams. The work presented is part of an optimization procedure based on iterative interaction with the process modelling of the whole cement plant with full oxy-fuel capture (not presented in this article). With retrofit application in mind, the objective was to reproduce a heat radiation profile to the clinker equivalent to that obtained in the air reference case. The optimized oxy-fuel case is characterized by a primary burner oxidizer of lower flow rate, but with higher oxygen concentration of up to 52.1% to generate the necessary heat in the near burner region. [ABSTRACT FROM AUTHOR]

Highlights • Systematic analysis of 4 CCS configurations, differing in the source of the regeneration steam and auxiliary power. • Sensitivity analysis for varying coal type, price, gas price, CO 2 sale price & tax, sorbent energy requirement and plant size. • The Petra Nova (PN) model has several advantages over the Boundary Dam (BD) model for new coal-fired power plants. • Overall CO 2 emission rate in the PN model is more than twice that of the coal-only case based on the BD model. Abstract SaskPower's Boundary Dam plant (Canada) and NRG's Petra Nova plant (USA) are the only two commercial-scale coal-fired power plants currently operational in the world that use carbon capture and storage (CCS) technology. While both CCS installations are retrofit projects that employ a post-combustion CO 2 capture system using advanced amines, the two plants differ significantly in their approach to providing the steam and electrical energy requirements of the capture system. This paper presents a comparative techno-economic evaluation of pulverized coal (PC) power plants equipped with the different CCS system configurations used in these two demonstration plants, as well as two additional design configurations that may be of interest. The results presented in this paper illustrate the conditions which favor one approach over the other, and thus provide insights for planning new large-scale CCS projects. [ABSTRACT FROM AUTHOR]

Copyright of Tecnologia em Metalurgia, Materiais e Mineração is the property of Associacao Brasileira de Metalurgia e Materiais and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract Anthropogenic Greenhouse Gases (GHG) emissions have increased since the pre-industrial era, driven by the economic and population growth. In the last decades, significant efforts have been made to develop cleaner and more efficient technologies able to control GHG emissions. In the field of combustion burners, this commitment strongly relies on the development of new and detailed numerical models, which allow a deep investigation of complex burner performance and a significant reduction of full-scale experimental costs. The knowledge previously acquired on the TEA-C coal burner CFD study is here expanded in the framework of the Be4GreenS project, targeting to the development of a new generation of burners. The new implemented model accounts for the detailed chemical and kinetic characterization of the pulverized coal together with the exact inner volume geometry of the experimental combustion chamber and the actual extension of the heat exchanging and refractory surfaces. In addition, the secondary and tertiary air registers are here numerically investigated. The outcome from the CFD analysis is validated against the experimental data. The NOx formation analysis is also provided. [ABSTRACT FROM AUTHOR]

Abstract Oxy-MILD (Moderate or Intensive Low Oxygen Dilution) combustion is an attractive technology for increasing combustion efficiency and reducing the nitric oxides with respect to the conventional combustion in traditional boilers or furnaces. This technology is a combination of MILD combustion, which exploits the initial preheating of combustion air up to 800÷1300 °C and the simultaneous recirculation of the hot flue gases, and of Oxy-Combustion, which uses pure oxygen (greater than 95% purity) as oxidant instead of air. The combination of both technologies is expected to bring synergetic effects: NO x reduction, CO 2 capture possibility, fuel flexibility and uniformity of heat fluxes and species concentrations. This study focuses, in particular, on the analysis, by a CFD approach, of the NO x emissions for Oxy-MILD combustion of pulverized coal in a new concept of industrial boiler. The boiler, fueled with a high-volatile coal, is equipped with five burners and three outlets of the combustion products, localized on the top wall. Each burner is made-up of a central pulverized coal jet surrounded by six preheated oxygen jets. This configuration allows the achievement of the MILD combustion in pure oxygen. Results show that the goal of NO x reduction with this combustion approach is achieved. A value of about 296 mg/Nm3@6%O 2 at the boiler exit is obtained under Oxy-MILD conditions, which is significantly lower than 600-800 mg/Nm3@6%O 2 obtained in a traditional boiler. [ABSTRACT FROM AUTHOR]

Ignitability, which is directly related to flame stability, is an important factor in pulverized coal combustion. In the current work, a laboratory test rig for comparative measurement of coal ignition properties is described. It has been designed for standard coal combustion conditions using air as oxidant. The measurement principle is described on the basis of experimental data gained from four “standard coals” of different rank and provenience. The results show the general tendencies known for the influence of coal rank. Higher volatile content in coal leads to lower ignition temperature. [ABSTRACT FROM AUTHOR]

Oxy-fuel combustion in pulverized coal (PC) and fluidized bed (FB) boilers is being increasingly investigated due to its potential use for carbon dioxide capture. The combustion conditions in the two types of unit differ significantly because of fuel size, furnace temperature, and fluid dynamics. These differences affect the change of combustion characteristics from air (O 2 /N 2 ) to oxy-fuel (O 2 /CO 2 ) conditions in PC and FB in different ways. In this paper, the oxy-fuel combustion behavior of a single sub-bituminous coal particle in PC is compared with that in FB conditions. The FB data were measured in our bench-scale FB test rig, whereas the PC data were collected from literature. The FB tests were performed at 1088 K with 0% vol < O 2 < 40% vol , using sub-bituminous coal with a diameter of 6 mm. An extensive list of parameters is compared, including the ignition-delay time, volatiles’ flame temperature, devolatilization time, burnout time and peak temperature of the coal particle. Results indicate that the impact of shifting from air-firing to oxy-firing affects the devolatilization, burnout times, and peak temperature in PC and FB differently: PC particles require higher concentration of oxygen than coarse particles for FB to attain similar results as in air-firing. However, the impact on the volatile flame temperature of shifting to oxy-fuel flame is similar in PC and FB. In general, the CO 2 atmosphere delays ignition compared to air-firing, particularly for coarse particles at low O 2 concentration. [ABSTRACT FROM AUTHOR]

The regeneration heat for a polyethyleneimine (PEI)/silica adsorbent based carbon capture system is first assessed in order to evaluate its effect on the efficiency penalty of a coal or natural gas power plant. Process simulations are then carried out on the net plant efficiencies for a specific supercritical 550 MWe pulverized coal (PC) and a 555 MWe natural gas combined cycle (NGCC) power plant integrated with a conceptually designed capture system using fluidized beds and PEI/silica adsorbent. A benchmark system applying an advanced MEA absorption technology in a NETL report (2010) is used as a reference system. Using the conservatively estimated parameters, the net plant efficiency of the PC and NGCC power plant with the proposed capture system is found to be 1.5% and 0.6% point higher than the reference PC and NGCC systems, respectively. Sensitivity analysis has revealed that the moisture adsorption, working capacity and heat recovery strategies are the most influential parameters to the power plant efficiency. Under an optimal scenario with improvements in increasing the working capacity by 2% points and decreasing moisture adsorption by 1% point, the plant efficiencies with the proposed capture system are 2.7% (PC) and 1.9% (NGCC) points higher than the reference systems. [ABSTRACT FROM AUTHOR]

The global warming and climate change are accelerated by the emissions of CH 4 , chlorofluorocarbon, and N 2 O gases along with CO 2 resulting from the use of fossil fuels. Recently, a new combustion technology that combines carbon-free ammonia (NH 3) fuel and coal has been proposed to reduce CO 2 emissions from thermal power plants. In this study, we examined the emission levels of NO and greenhouse gas N 2 O from the existing coal-fired and future carbon-neutral coal/ammonia co-fired thermal power plants. As a result, a correlation between the amounts of NO and N 2 O gases generated during combustion in the furnace of a thermal power plant was established, and possible relationships between NO and N 2 O emissions during the selective non-catalytic reduction (SNCR) and selective catalytic reduction (SCR) of NOx were experimentally analyzed. In addition, a linear correlation between the CO and N 2 O concentrations was observed. The air-staged combustion during SCR (300 °C, urea) produced the lowest total emission concentration of NO and N 2 O (9 ppm) under the utilized conditions. The findings of this study can help control the emission levels of air pollutant NO and greenhouse gas N 2 O throughout the entire process of thermal power plants. [Display omitted] • NH 3 solution enhances N 2 O generation to make reduction reaction in the furnace. • Emission of NO and N 2 O was the most minimized under air-staged combustion with SCR. • Increase of SNCR and SCR temperature promotes NO reduction and N 2 O decomposition. [ABSTRACT FROM AUTHOR]

• Implementation of oxy-fuel combustion technology to existing industrial boilers. • Oxy-fuel combustion technology makes it easier to capture CO 2. • CFD modelling of oxy-fuel combustion of pulverized coal in an industrial boiler. • Dependences of oxy-fuel combustion indices on operating parameters were obtained. • Parameters of the blast to ensure the normal operation of the boiler were determined. Numerical studies of the processes of oxy-fuel combustion of pulverized coal (PC) in an industrial boiler BKZ 500–140–1 (with a capacity of about 400 MW) were carried out in this work. The proposed comprehensive mathematical model was tested based on data from a full-scale experiment (2.4 MW laboratory stand) of oxy-fuel combustion of PC. The conducted comparison has shown a good agreement of the calculation results with the experimental data. A detailed comparative analysis of the effect of the operating modes of the BKZ 500–140–1 industrial boiler during oxy-fuel combustion of coal on physical and chemical processes and the level of harmful emissions (NO x , CO 2) was performed for the first time. The effect of oxygen concentration and CO 2 /H 2 O ratio in the blast on the processes of ignition and combustion of fuel in a nitrogen-free environment has been studied. It is shown that when nitrogen in the blast composition is replaced with flue gases without changing the oxygen concentration in the boiler under study, the average temperature in the furnace volume declines, as well as the average heat flux at the walls decreases from 87.35 to 70.32 kW/m2. To achieve the standard operating parameters of the BKZ 500–140–1 industrial boiler, it is necessary to increase the oxygen concentration in the blast from 15.4 to 19.7 vol.% (i.e. by 28%). The implementation of the oxy-fuel combustion technology on a steam boiler leads to a decrease in the NO x concentration in flue gases from 480 to 273 mg/m3. [ABSTRACT FROM AUTHOR]

The paper presents a concept of a new cyclone furnace for combustion of solid fuel under conditions of oxy-fuel combustion, which was used in the past in cyclone combustion chambers. The principal factors and determinants of operation and performance of such combustion chambers were presented. Possible variants of integration of this combustion chamber with a pulverized-fuel boiler were also discussed. [ABSTRACT FROM AUTHOR]

Coal seams that are prone to strong outbursts have low strength and cause heavy structural damage to the seam. Their outburst risk is highly related to the release of the adsorbed coalbed gas, which is controlled by the gas desorption and diffusion characteristics of coal. In the Haizi Coal Mine, China, an extremely high gas outburst risk was detected, and the coals from this area were found to have an unprecedented high degree of fragmentation and were present in the pulverized state. To explain the pulverization characteristics of the pulverized coal, the related physical parameters were investigated; the gas desorption and diffusion properties of the pulverized coal were analyzed and compared with those of the unpulverized coal. The results indicated that the pulverized coal could easily reach the required degree of fragmentation for a coal and gas outburst to occur. Furthermore, the pore volume and specific surface area of the pulverized coal differed according to the coal particle size. Compared with the unpulverized coal, the gas desorption and diffusion properties of the pulverized coal were largely varied, and the pore structure of the pulverized coal was much simpler. The formation of pulverized coal is believed to be closely related to complex geological conditions. [ABSTRACT FROM AUTHOR]

This paper assesses operational strategies for deploying flexible CO 2 capture at three generic black coal fired power plants with distinct dispatch profiles. Flexible operating modes involving constant partial CO 2 capture, part-time capture, and variable capture are examined in conjunction with seasonal effects of summer and winter. The three generic dispatch profiles are selected to represent typical black coal base load power plants in Australia and black coal power plants in Germany and perhaps future UK base load power plants in 2011. The results show that for a generic 700 MW subcritical power plant, operating under variable capture mode results in the highest amount of CO 2 captured and avoided and thus the lowest cost. The estimated cost of CO 2 avoided ranges from about $70 to $150 per tonne of CO 2 avoided using variable capture, increasing to $186 to $226 per tonne of CO 2 avoided for constant partial capture. The flexible capture modes investigated can reduce the overall CO 2 emissions of a power plant by up to 50%. [ABSTRACT FROM AUTHOR]

In this paper the results obtained by the numerical method of modeling of Ekibastuz coal burning in BKZ-420 combustion chamber of Kazakhstan Power Plant are presented. They are devoted to the numerical simulation of combustion processes in the furnace boiler BKZ-420. Boiler's steam generates capacity equal 420 T/h. Boiler has six vertical pulverized coal burners arranged in two levels with three burners on the front wall of the boiler. High ash, low-grade coal from Ekibastuz burned in the furnace. Its ash content is 40%, volatile - 24%, humidity-5%, highest calorific value is 16750 kJ/kg. Milling dispersity of coal was equal to R90 = 15%.It was shown in this research that the most intense burning is observed in the central part of the chamber where the flow temperature reaches about 980 °C and it is seen that the temperature reaches a peak in the cross sections of the burners location. The combustion reaction there occurs more intensively. [ABSTRACT FROM AUTHOR]

The technical performance and cost effectiveness of white wood pellets (WWP) combustion in comparison to three types of coal namely U.S., Russian and Colombian coals are investigated in this study. Post-combustion capture and storage (CCS) namely with amine FG+, and oxy-fuel with carbon capture and storage (oxy-fuel) are applied to a 650 MW pulverized combustion (PC) plant. The impacts of the Renewable Obligation Certificate (ROC) and carbon price (CP) policy in accelerating the CCS deployment in the framework of GHG emissions mitigation, are also evaluated. The operational factors affecting CCS costs and emissions in the power generation plants are taken into consideration, hence, the Integrated Environmental Control Model (IECM 8.0.2) is employed for a systematic estimation of plant performance, costs and emissions of different scenarios of fuel and CCS technologies. This study showed that the utilization of white wood pellets (WWP) in electricity generation can annually avoid about 3 M tonnes CO 2 emissions from a 650 MW power plant. However, this mitigation process had impact on the plant efficiency and the cost of electricity. Further, the BECCS using white wood pellets has showed a better efficiency and lower cost of electricity with the oxy-fuel technology than the post-combustion CCS technology. However, in order to boost biomass energy CCS (BECCS) deployment with the WWP, an increase of the ROC for biomass power plants, or, an increase of the carbon price for the coal power plants is recommended. It was found that, the sensitivity of COE towards the ROC was higher than towards the carbon price variation. This result can be interpreted as the ROC has more positive impact than the carbon price, on the COE from the point of customers view without adding more burdens on the power generation companies. [ABSTRACT FROM AUTHOR]

The purpose of the present study is to clarify the effects of temperature, initial SO 2 concentration and steam addition on SO 3 formation under oxy-fuel combustion. The experiments consisted of two parts. The first part was the homogeneous experiment conducted with the simulated flue gas in a horizontal tube furnace. In order to further study the formation characteristics of SO 3 in the heterogeneous gas atmosphere, the other part of the experiments was carried out by using a high-sulfur coal and a low-sulfur coal respectively in a drop tube furnace. The experiment results indicated that SO 3 concentration increased first but then decreased with the temperature increasing, and the maximum SO 3 concentration appeared at around 950 °C. The increase of initial SO 2 concentration could significantly enhance SO 3 formation. But the injected steam inhibited SO 3 formation in all test cases obviously, as the injection of steam could increase the kinds of the radical pool compositions in the flue gas, which might involve more complex interactions with the formed SO 3 during wet recycling. Moreover, compared to the former homogeneous experiment, the latter presented a more intense inhibiting behavior, which was probably attributed to the more diversification of the radical pool compositions in pulverized-coal combustion. [ABSTRACT FROM AUTHOR]

• Pressurized oxy-fuel combustion performance of a typical bituminous coal is investigated. • The thermodynamics parameters and the most probabilistic kinetic model for the pressurized oxy-fuel combustion process are analyzed. • Elevating pressure can significantly improve the combustion performance of coal but the promotion effect gradually alleviates. • The ignition mechanism transforms from heterogeneous to homogeneous when the oxygen concentration reaches 50% at 0.5 MPa. Pressurized oxy-fuel combustion is one of the emerging clean technologies that can efficiently separate and recover CO 2 , and this combustion mechanism differs significantly from atmospheric air combustion. In this paper, the effects of reaction conditions such as total pressure, oxygen concentration and atmosphere gas composition on the combustion characteristics of Xinjiang Bostan coal were investigated using thermogravimetric methods. Furthermore, the thermodynamics parameters and the most probabilistic kinetic model for the pressurized oxy-fuel combustion process were explored. The results showed that the system pressure rising from 0.1 to 1 MPa could enhance the combustion process of coal; however, when the system pressure exceeds 0.5 MPa, the promoting effect is clearly weakened. The ignition mechanism transforms from heterogeneous to homogeneous when the oxygen concentration reaches 50% at 0.5 MPa. The mechanism functions of pressurized oxy-fuel combustion reaction varied as the reaction progressed. In addition, the rise of pressure and oxygen concentration correspond to the higher chemical reaction order of pulverized coal combustion and the pressure has less influence on the reaction mechanism than oxygen concentration. The results obtained may assist with the optimization of pressurized oxy-fuel combustion and guide its industrial applications. [Display omitted] [ABSTRACT FROM AUTHOR]

The objective of this paper is to assess the current costs of CO 2 capture and storage (CCS) for new fossil fuel power plants and to compare those results to the costs reported a decade ago in the IPCC Special Report on Carbon Dioxide Capture and Storage (SRCCS). Toward that end, we employed a similar methodology based on review and analysis of recent cost studies for the major CCS options identified in the SRCCS, namely, post-combustion CO 2 capture at supercritical pulverized coal (SCPC) and natural gas combined cycle (NGCC) power plants, plus pre-combustion capture at coal-based integrated gasification combined cycle (IGCC) power plants. We also report current costs for SCPC plants employing oxy-combustion for CO 2 capture—an option that was still in the early stages of development at the time of the SRCCS. To compare current CCS cost estimates to those in the SRCCS, we adjust all costs to constant 2013 US dollars using cost indices for power plant capital costs, fuel costs and other O&M costs. On this basis, we report changes in capital cost, levelized cost of electricity, and mitigation costs for each power plant system with and without CCS. We also discuss the outlook for future CCS costs. [ABSTRACT FROM AUTHOR]

Co-combustion of Biomass is a promising greenhouse gases (GHG) abatement technology. This study presents a numerical modeling of co-combustion of coal and Biomass firing under air and oxy-fuel conditions in a small scale furnace. Co-firing conditions are varied with the Biomass sharing considering 20%, 40% on mass basis. Level of confidence is achieved by comparing the model-predicted peak radiative heat flux against the experimental data. Results are presented comparing the flame temperature distribution, species concentration for different cases. Unburned Carbon in ash (CIA) is predicted for different cases and reasonable agreement has been obtained. An improved burnout was observed in oxy-fuel cases. No significant change in CO 2 concentrations with the increase of biomass contribution to the total fuel input proves that biomass is CO 2 -neutral energy source. [ABSTRACT FROM AUTHOR]

Oxy-steam combustion technology is regarded to be the next generation of oxy-fuel combustion technology. Because the physical and chemical properties of steam are very different from that of CO 2 or N 2 , especially its reactivity, the ignition characteristics of coal in oxy-steam combustion are expected to be different from those in conventional combustion or O 2 /CO 2 recycled combustion. This paper presents experimental investigations of the ignition behaviors of coal in O 2 /N 2 and O 2 /H 2 O atmospheres using different oxygen fractions (21%, 30%, 35%, 40% and 50%). Ignition experiments were performed in a drop tube furnace. The ignition behaviors were recorded using a high-speed camera and a two-color pyrometer. According to the images of the ignition, the pulverized coals ignite homogeneously in all cases. The ignition of pulverized coal in the O 2 /H 2 O atmospheres occurs sooner than in the O 2 /N 2 atmospheres at identical oxygen fractions. A high concentration of steam may enhance the steam gasification reaction (C + H 2 O → CO + H 2 ) and the steam shift reaction (CO + H 2 O → CO 2 + H 2 ) in O 2 /H 2 O atmospheres. These two reactions can form a large amount of H 2 and CO in O 2 /H 2 O atmospheres in the gaseous mixture around the coal particle. This result is beneficial to reducing the ignition delay times of volatiles mixtures in O 2 /H 2 O atmospheres. [ABSTRACT FROM AUTHOR]

Pulverized coal injection (PCI) into blast furnace tuyere using two novel oxygen-coal lances has been designed by MCC Company. In this paper, a three-dimensional multi-phase model with Discrete Particle Model (DPM) approach has been developed to examine the performance of the novel oxygen-coal lance for PCI operation. Simulation conditions and properties of the PCI were obtained from the real operation conditions of the blast furnace of 580 m 3 with molten iron output of 1775 t/d in the industrial experimental base of MCC Incorporation. The simulation results of novel PCI style were also compared with the results of traditional one. Results show PCI using sing coal lance and single oxygen lance pattern is inferior to the conventional PCI mode. Its disadvantages include low BR increase, poor oxygen utilization level and potential damages to the tuyere. PCI using twin oxygen-coal lances is superior to the conventional PCI pattern. Its advantages include doubled burnout ratio, satisfying oxygen consumption level in the raceway and high temperature zone in a safe distance from the nozzle. [ABSTRACT FROM AUTHOR]

In this paper, pulverized coal from industry was used as the experimental material and sieved into seven samples with different particle size. The effect of particle size on the flow properties of pulverized coal was investigated. An annular shear cell was used to measure angle of internal friction, angle of effective internal friction, cohesion and angle of wall friction, and a transparent Perspex hopper was used to determine the discharge characteristics of pulverized coal. The experimental results showed a significant effect of particles size on the cohesive and angle of wall friction rather than on the angle of internal friction. Jenike's procedure was used to predicate the flow pattern of pulverized coal with different particle size, which linked with the discharge experiment. Three regions including arching, unstable-flow and mass-flow were obtained based on the analysis of weighting curves and a progressive transition from blocking to unstable flow and to mass flow was observed as the particle size increased. In addition, the failure properties of pulverized coal was investigated which supported the region division. The investigation showed that the effect of particle size on the flow properties of pulverized coal is diversity and rheological test results can reflect flow properties of pulverized coal to some extent. [ABSTRACT FROM AUTHOR]

The chemical composition, microstructure and size distribution of pulverized coal and fly ash samples from SCGP(Shell Coal Gasification Process) devices of four different regions were measured using an energy dispersive spectrometer, a scanning electron microscope, and Coulter particle analyzer. The paper aims to analyze the influence of pulverized coal on characteristics of fly ash. The energy dispersive analysis showed the main elements of chemical composition of fly ash and pulverized coal were C, O, Si, Al, and small amounts of metal elements. The difference of chemical composition of pulverized coal samples illustrates the types of coal were different. The similarity in chemical composition of four types of fly ash was due to the same technical process. Scanning electron microscope measurements showed particulate microstructures of four samples of pulverized coal were irregular, however, particulate microstructures of samples of fly ash were all spherical. The surface of most spherical particles had microspheres that were often agglomerated together. This phenomenon indicated that particulate microstructures of pulverized coal had no influence on particulate microstructures of fly ash. The size distribution showed median size of four pulverized coal samples were 31.59 μm, 28.85 μm, 25.57 μm and 20.62 μm. Median size of four fly ash samples were 4.07 μm, 3.89 μm, 3.45 μm and 3.04 μm. The particle size of fly ash increases with the growth of particle size of pulverized coal. The crests of particle size distribution curves of pulverized coal were not obvious due to the grinding evenness of coal were low. Particle size distribution curves of fly ash were opposite. This phenomenon indicates that uniform degree of fly ash is not affected by coal grinding evenness. In conclusion, the particle size of pulverized coal is the main influencing factor on the characteristics of fly ash while the influences of type of coal, particulate microstructures and grinding evenness of pulverized coal are not so much. Particle size of fly ash has a vital influence on high-temperature ceramic filters in SCGP. Controlling particle size of pulverized coal has a certain guiding significance to reducing the working load and extending the life of filter elements. [ABSTRACT FROM AUTHOR]

Pulverised coal preparation system (Coal mills) is the heart of coal-fired power plants. The complex nature of a milling process, together with the complex interactions between coal quality and mill conditions, would lead to immense difficulties for obtaining an effective mathematical model of the milling process. In this paper, vertical spindle coal mills (bowl mill) that are widely used in coal-fired power plants, is considered for the model development and its pulverised fuel flow rate is computed using the model. For the steady state coal mill model development, plant measurements such as airflow rate, differential pressure across mill etc., are considered as inputs/outputs. The mathematical model is derived from analysis of energy, heat and mass balances. An Evolutionary computation technique is adopted to identify the unknown model parameters using on-line plant data. Validation results indicate that this model is accurate enough to represent the whole process of steady state coal mill dynamics. This coal mill model is being implemented on-line in a 210 MW thermal power plant and the results obtained are compared with plant data. The model is found accurate and robust that will work better in power plants for system monitoring. Therefore, the model can be used for online monitoring, fault detection, and control to improve the efficiency of combustion. [ABSTRACT FROM AUTHOR]

Oxy-fuel combustion is one of competitive and promising carbon capture technologies for restraining CO 2 emissions from power plants. Dynamic simulation of oxy-combustion system, which is essential for gaining its dynamic characteristics, can help to evaluate and improve process design, and to develop control system and operational strategies. This paper focuses on dynamic simulation and control design for a conceptual 600 MWe oxy-combustion pulverized-coal-fired boiler. The steady-state model using a pseudo coal to substitute real coal is established, validated, and then transformed into the dynamic model which uses pressure-driven solution. The control system, which aims to automatically regulating flue gas O 2 concentration within reasonable range (2–7 mol.% in this study), is designed and applied to the dynamic boiler model. Three planned disturbances of load change, oxygen purity (from cryogenic air separation unit) ramp change and air in-leakage (from boiler) step change are conducted. Detailed dynamic behavior from water side and flue gas side is obtained and analyzed to help engineering operation in real plant. Mode switching process and alternative control strategy are simulated and discussed. Comprehensive dynamic model with specified control system provides possibility to study the dynamic characteristics of full-train oxy-combustion power plants. [ABSTRACT FROM AUTHOR]

Pulverized coal combustion technology in O 2 /CO 2 atmosphere is widely accepted as a new combustion technology. This method does not only recycle CO 2 , but also lowers NO x emission. However, pulverized coal combustion technology has several problems such as pulverized coal ignition delay, low flame temperature, and incomplete burning. Such issues have attracted the attention of the local and international academic communities. This study adopts a numerical simulation to analyze the combustion characteristics of conventional sized pulverized coal (70 μm) mixed with superfine pulverized coal (20 μm) in O 2 /CO 2 atmosphere. The influences of co-combustion of two sizes pulverized coal on ignition, combustion flame structure, and NO x generation were analyzed. Results showed that the co-combustion of superfine and conventional-sized pulverized coal can enhance the ignition and combustion performance of pulverized coal in O 2 /CO 2 atmosphere. The improved ratio of superfine pulverized coal promotes ignition process of pulverized coal and combustion intensity. Moreover, co-combustion can decrease NO x generation. As the ratio of superfine to conventional sized pulverized coal increases, NO x emission decreases. The reduction effect of NO x is most significant when the ratio of superfine to conventional sized pulverized coal increases from 30% to 50% and the co-combustion of superfine and conventional sized pulverized coal in O 2 /CO 2 atmosphere can simultaneously improve combustion performance and reduce NO x discharge. [ABSTRACT FROM AUTHOR]

Oxy-steam combustion is proposed as an alternative for the next generation oxy-fuel combustion technology. In order to justify the economic feasibility of this novel oxy-fuel combustion, a conventional 600 MWe pulverized-coal-fired power plant in China is selected to be retrofitted to oxy-steam combustion and O2/CO2 recycled combustion separately, whilst the O2/CO2 recycled combustion system serves as the base case for comparisons. The modeling and simulation of these two systems are carried out with Aspen Plus version 11.1. Simulation results indicate that on the same boundary conditions, the mass flow of the main steam and reheated steam in the oxy-steam combustion system must be reduced by 0.84%, which makes the net energy efficiency of the oxy-steam combustion system decrease by 0.15%. The comparative exergy analyses reveal that the net exergy efficiency of the oxy-steam combustion system is 0.153% lower than that of the O2/CO2 recycled combustion system. The marked increase of the exergy destruction happening in the oxy-steam combustion furnace is the fundamental cause of the decrease of the exergy efficiency. [ABSTRACT FROM AUTHOR]

We performed a study to determine whether flue gas bypass and solvent storage can increase the profitability of a power plant equipped with post-combustion carbon capture technology. By increasing flexibility, these technologies allow increased output when electric energy prices are high. We used the Integrated Environmental Control Model to characterize cost and operational parameters of a pulverized coal (PC) plant with both amine and ammonia carbon-capture systems, as well as a natural gas combined cycle plant with amine capture. We constructed profit-maximization operating models with both perfect and imperfect information about electric energy prices in a large electricity market in the Eastern United States. We optimized the size of the regenerator and solvent storage vessels to maximize profitability. Results indicate that the profitability benefits of flexible CCS range from 0 to 35%. Most of the potential benefit is capital savings from allowing the regenerator to be undersized. The benefits of flexible CCS were found to decline with increasing CO2 prices, with steady-state units preferable above a CO2 emissions price of $40/tonne. Flexible CCS was never optimal when the overall plant was profitable. While flexible CCS can boost profitability under policies that force plants with CCS to be built even where they are not profitable, it is less relevant under market-based policies that incentivize CCS through CO2 prices. [ABSTRACT FROM AUTHOR]

The co-combustion of pulverised coal and biomass is increasingly being used for environmental reasons, and a number of computational fluid dynamic investigations are being undertaken to understand the details of the combustion process. These investigations assume that the particle flow entering the burner is uniformly distributed across the burner mouth or inlet. In this paper, this assumption is examined for an industrial burner by numerically simulating the fuel particle flows in the tube leading to the burner mouth. While there is evidence of maldistribution of the particles at the burner mouth, it is concluded from the flame data that this effect does not significantly influence the combustion flame in the furnace for the cases investigated. [ABSTRACT FROM AUTHOR]

Abstract: It is important to be aware of the particle size distribution and composition of ash in coal combustion for prediction and control of ash deposition behavior, which results in the degradation of boiler performance via fouling and slagging. To elucidate fragmentation and coalescence behavior of mineral particles in a pulverized coal combustion process, char particles during the combustion reaction were sampled and analyzed for their particle size distribution and composition using a drop tube furnace. CCSEM analysis was conducted to identify included and excluded minerals in sampled char particles. Three coal samples having different char structures and ash melting temperatures were tested to estimate the effect of the physical properties of ash on fragmentation and coalescence behaviors of mineral particles. With the progress of combustion, the number of included mineral particles decreased due to their separation from char particles, leading to the increase of the number of excluded mineral particles. The total number of particles decreased with the progress of combustion. Some of particles were agglomerated, and some of them were fused to each other. These behaviors were less obvious for coal which experienced network structure of char particles during its combustion process. On the other hand, minerals in coal characterized by low melting point ash were rounded off during the coal combustion process. Fractions of included mineral were higher at smaller particle sizes, and they decreased with the progress of combustion. Elemental compositions of fused particles in coal characterized by low melting point ash are attributed to that of aluminosilicate. [Copyright &y& Elsevier]

Abstract: A particle population balance model was developed to predict the oxidation characteristics of an ensemble of char particles exposed to an environment in which their overall burning rates are controlled by the combined effects of oxygen diffusion through particle pores and chemical reactions (the zone II burning regime). The model allows for changes in particle size due to burning at the external surface, changes in particle apparent density due to internal burning at pore walls, and changes in the sizes and apparent densities of particles due to percolation type fragmentation. In percolation type fragmentation, fragments of all sizes less than that of the fragmenting particle are produced. The model follows the conversion of particles burning in a gaseous environment of specified temperature and oxygen content. The extent of conversion and particle size, apparent density, and temperature distributions are predicted in time. Experiments were performed in an entrained flow reactor to obtain the size and apparent density data needed to adjust model parameters. Pulverized Wyodak coal particles were injected into the reactor and char samples were extracted at selected residence times. The particle size distributions and apparent densities were measured for each sample extracted. The intrinsic chemical reactivity of the char to oxygen was also measured in experiments performed in a thermogravimetric analyzer. Data were used to adjust rate coefficients in a six-step reaction mechanism used to describe the oxidation process. Calculations made allowing for fragmentation with variations in the apparent densities of fragments yield the type of size, apparent density, and temperature distributions observed experimentally. These distributions broaden with increased char conversion in a manner that can only be predicted when fragmentation is accounted for with variations in fragment apparent density as well as size. The model also yields the type of ash size distributions observed experimentally. [Copyright &y& Elsevier]